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Free Radicals &
Antioxidants
614 351 Toxicology
Supatra Porasuphatana, Ph.D.
Contents
• Introduction of oxygen toxicity
• Free radicals/Reactive oxygen species
• Sources of free radical formation
• Types of free radicals
• Free radical toxicity
• Free radical and diseases
• Antioxidants
Page 2
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Oxygen Toxicity
• Evidences
– High pressure oxygen inhibits bacterial growth
– High pressure oxygen causes acute CNS
toxicity
– Oxygen exposure in premature babies
– Experiments – Tissue damages by oxygen
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Free Radicals
“any species capable of independent existent that
contains one or more unpaired electrons”
Example :



O  H

Hydroxyl radical ( OH)
Radicals can be formed by…
1.
The LOSS of a single electron from a non-radical,
or by the GAIN of a single electron by a non-radical
2.
The breakage of covalent bond ‘homolytic fission’
A  B
Page 4
A + B 
Example : H2O
H  +  OH
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Free Radical Nomenclature
•
A free radical is denoted by a superscript
dot to the oxygen (or carbon)
–
•
e.g., HO, NO, CH3
If a free radical is a charged species, the
dot is put and then the charge
–
e.g., O2-
(See “Free Radical Nomenclature, Suggestions” by
Buettner, G.R., Schafer, F.Q.)
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Free Radicals
*2p
p*2p
p2p
2p
*2s
2s
*1s
1s
Ground-state O2 Singlet O2
(3g-O2)
(1DgO2)
Page 6
Singlet O2
Superoxide Peroxide ion (Singlet
1g+O )O2
2
2
(O2 )
(1g+O
(O2-)
2)
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
O




O

Oxygen (O2)
Reactive Oxygen Species


• Radicals – Hydroxyl radical

O  H
H
• Molecules – Hydrogen


peroxide




O  O 


• Ions – Hypochlorite ion
• Superoxide anion – which
is both ion and radical
Page 7


Hydroxyl radical (OH)

H

O  H
-


O


Hydrogen peroxide (H2O2)



-
Cl 


 O   O


-
Hydroxy anion (OH-)
Hypochlorite anion (OCl-)
-
Superoxide anion (O2 )
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Types of Free Radicals
• Oxygen-centered radicals
– Singlet oxygen, superoxide, hydroxyl radicals
• Sulfur-centered radicals
– Thiyl radical (RS•)
• Carbon-centered radicals
–
•
CCl3, CH2•CHOH
• Nitrogen-centered radicals
– NO•, R2NO•
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Oxygen-Centered Radicals
• Reactive Oxygen Species (ROS)
Radicals
Non-Radicals
Superoxide, O2-
Hydrogen peroxide, H2O2
Hydroxyl, HO
Hypochlorous acid, HOCl
Peroxyl, ROO
Ozone, O3
Alkoxyl, RO
Singlet oxygen, 1Dg
Hydroperoxyl, HOO
Peroxynitrite, ONOO-
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Superoxide Radicals
-
• Generation of superoxide (O2 )
– The addition a single electron to the ground-state
molecule (O2 + eO2 -)

• Biological generation of O2

-
– Mitochondrial electron transport chain
– Enzymatic reduction of oxygen (O2)
– Xenobiotic metabolisms (redox cycling)
– Respiratory burst (phagocytes)
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Mitochondrial Electron
Transport Chain
• The most important source of O2- in vivo in
most aerobic cells
• Mitochondrial functions
– Oxidation of NADH, FADH2, -oxidation of fatty
acids, other metabolic pathway
– ‘Electron transport chain’
in the inner mitochondrial
membrane
– Energy released is used for
ATP synthesis
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Superoxide Production from
Mitochondrial Electron Transport Chain
‘Leaking’ of electron (to oxygen) during electron transport leads to
the formation of O2- (O2 + ePage 12
O2-)
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Biological Generation of Superoxide
• Enzymatic reduction of oxygen
XOD
Xanthine/hypoxanthine
Uric acid
O2-
O2
[XOD = xanthine oxidase]
• Redox cycling : Paraquat
NADPH
Oxidized
cytochomre
P450
reductase
H3C
N
NADP
Reduced
cytochomre
P450
reductase
H3C
+
N
•
+
N
CH3
O2
+
N
CH3
O2  -
e-
Paraquat
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Respiratory Burst
• Myeloperoxidase
– Oxidizes Cl- to hypochlorous acid
– Chronic granulomatous disease
• NADPH oxidase enzyme
NADPH
O2
•
outside
inside
O2
-
•
NADPH
NADP+
... O2
. -
NADP+
O2
Phagocytic vacuole (phagosome)
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Respiratory Burst
NADPH oxidase complex
• Cytoplasmic proteins
(p47, p67, gp91, p22)
• NADPH
NADP+ + H+
• Electron is transferred
from NADPH to O2, resulting
in the formation of O2[NADPH : Reduced Nicotinamide Adenine Dinucleotide Phosphate]
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Hydroxyl Radical (HO )

• Highly reactive oxygen radicals
• Formation of hydroxyl radicals in biological
systems
– Ionizing radiation
– Reaction of metal ions with hydrogen peroxide
(Fenton reaction)
– Formation of hydroxyl radical from ozone (O3)
• Reactions of hydroxyl radicals
– Hydrogen atom abstraction
– Addition
– Electron transfer
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Fenton Reaction
•
Discovered by Fenton (1894)
•
“A mixture of hydrogen peroxide and an iron(II) salts causes the
formation of hydroxyl radical”
•
Fe2+ + H2O2
intermediate complex
Fe3+ + OH- + HO
Fe3+ + H2O2
intermediate complex
Fe2+ + O2 - + 2H+
Haber-Weiss reaction
Fe2+ + H2O2
Fe3+ + OH- + HO
Fe3+ + O2 -
Fe2+ + O2
Net : O2 + H2O2
-
Page 17
metal
catalyst
O2 + HO + OH23/05/60
Nitrogen-Centered Radicals
• Nitric oxide (NO)
– Endothelial derived-relaxing factor (EDRF)
– Generated from the catalysis of L-arginine by
nitric oxide synthase (NOS) enzymes
– Functions
• Vascular function, platelet aggregation, immune
response, neurotransmitter, signal transduction
• cytotoxicity
– NO + O2Page 18
ONOO- (highly toxic)
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Sources of Free Radicals
• Endogenous sources of free radicals
– Oxidative metabolic transformation
• Mitochondrial respiratory chain
• Oxygen burst (respiratory burst) during
phagocytosis
• Eicosanoid synthesis
• Enzymatic reactions (oxygenases, oxidases)
– Xenobiotic metabolism (redox cycling)
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Sources of Free Radicals
• Exogenous sources
of free radicals
– Ionizing radiation
– Ultraviolet radiation
– Ultrasound
– Chemicals, tobacco
smoke, etc
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Roles of Free Radicals in
Biological Systems
• Enzyme-catalyzed reactions
• Electron transport in mitochondria
• Signal transduction & gene expression
• Activation of nuclear transcription factors
• Oxidative damages of molecules, cells, tissues
• Antimicrobial actions
• Aging & diseases
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Oxidative Stress
• Damages caused by free radicals/reactive
oxygen species
• Cellular damages at different levels
(membrane, proteins, DNA, etc) lead to cell
death, tissue injury, cellular toxicity, etc
• Reduction of antioxidants
(cause & consequence ?)
• Prevented by the reduction of free radicals,
inhibition of free radical formation
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Oxidative Stress
O2
Non-enzymatic sources
OH
Mitochondrial respiratory chain
Glucose autoxidation
Enzymatic sources
NADPH oxidase
Xanthine oxidase
Cyclooxygenase
O2-
Fenton reaction
(Fe or Cu)
SOD
H2O2
GSH
GPx
NO
Catalase
GSSG
ONOOPage 23
H2O + O2
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Free Radical Toxicity
• Causes of free radical toxicity
– Increase production of free radicals
– Decrease level of defense system
antioxidants)
(e.g.,
• Lipid peroxidation
• DNA damage
• Protein oxidation
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Lipid Peroxidation
1. Initiation of first-chain reaction
• Abstraction of H+ by ROS ( OH)
• Formation of lipid radical (LH )
• Formation of peroxyl radical (LOO , ROO )
•
•
•
•
2. Propagation
• H+ abstraction by lipid peroxyl radical (LOO )
•
3. Termination
• Radical interaction
Page 25
non-radical product
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I
Hydrogen abstraction
•
-H •
Molecular rearrangement
Conjugated diene
•
O2 Oxygen uptake
Peroxy radical: abstract
H• rom another fatty acid
causing an autocatalytic
chain reactions
P
O
O
•
H•
Lipid hydroperoxide
Cyclic peroxide
O
Page 26
O
I Initiation
H
P Propagation
Cyclic endoperoxide
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Products of Lipid
Peroxidation
Reactive Oxygen Species
Lipid peroxides
Alkanes
Aldehyde
products
Conjugated dienes
Malondialdehyde
(MDA)
n-aldehydes
Page 27
,-unsaturated
aldehydes
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PGF2-Isoprostane
• A group of prostaglandin (PGF2)-like
compounds produced by non-enzymatic free
radical-induced peroxidation of arachidonic
acid
• Reliable biomarker of oxidative stress in vivo
–
–
–
–
–
–
Specific product of lipid peroxidation
Stable compound
Detectable level in biological samples
Level increases during oxidative injury
Formation is modulated by antioxidant status
Not affected by lipid contents from diet
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Oxidative DNA Damage
• Correlation with cancers and diseases
• Oxidative DNA lesions by
– Direct attack
– Indirect activation of endonuclease enzymes
• Oxidative modification of bases – mutation
• Oxidative modification of sugar moieties –
DNA strand break
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A computer image depicts a
hydroxyl radical attacking the
sugar on the back bone of a
DNA molecule
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Oxidative DNA Damage
O
N
N
O
O
P
O
N
O
NH2
N
O
O
O
N
O
P
O
O
N
O
O
Page 32
O
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Oxidative DNA Damage
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Oxidative DNA Products
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Oxidative DNA Damage
• 8-Hydroxyguanine (8-OH-Gua)
– GC
TA transversions
(frequently detected in p53 gene
and ras protooncogene)
• 2-Hydroxyadenine (2-OH-Ade)
• 8-Hydroxyadenine (8-OH-Ade)
• 5-Hydroxycytosine (5-OH-Cyt)
• 5-Hydroxyuracil (5-OHUra)
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Oxidative DNA Damage
• Abstraction of H+ atom from
carbon atoms of sugar molecules
• Disproportionations and
rearrangement lead to
C-C bond fragmentation and
DNA strand break
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Protein Oxidation
• Protein targets
– Receptors, transport proteins, enzymes, etc
– Secondary damage – autoimmunity
• Protein oxidation products
– Protein carbonyl group, 3-nitrotyrosine,
other oxidized amino acids
• Most susceptible amino acids
– Tyrosine, histidine, cysteine, methionine
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Protein Oxidation
Oxidative protein degradations
Modifications of
amino acid chain
Modifications of
prosthetic group
of enzymes
Protein aggregation
Protein fragmentation
Activations of protease enzymes
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Protein Oxidation
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Free Radical Toxicity
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Free Radicals and Diseases
• Cancer
• Inflammation/Infection
• Ischemia-reperfusion injury
– Cardiac ischemia-reperfusion injury
– Cerebral ischemia-reperfusion injury
• Neurodegenerative diseases
• Cardiovascular diseases
• Aging
• Others (e.g., drug/chemical-induced toxicity, etc)
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Oxidative DNA Damage & Cancer
ROS can attack
deoxyribose, purine,
and pyrimidine bases in
DNA resulting in DNA
strand breaks
DNA strand breaks
induced by OH cause
deletions and point
mutations
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Oxidative DNA Damage & Cancer
Oxidative DNA damage
Point mutation
Chromosomal aberrations
DNA strand breaks
Oxidative modification of DNA
Base modifications
Sequence change
Activation of kinases
Activation of protooncogenes
Inactivation of tumor suppressor genes
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Oxidative DNA Damage & Cancer
Hydroxyl radical-induced
DNA oxidative damage
• Hydroxylation of guanine
residue (dG) to produce
8-OH-dG is the most common
biomarker of OH-induced DNA
damage
• Detectable in cell, tissues,
urine
• Levels can be modulated by
antioxidants
Page 44
Figure : 8-OH-dG content in DNA
samples isolated from control ( ),
myeloma ( ) tissues, and
lymphocytes ( ) of myoma
patients. (Ref. Foskinski, M,. et al. Free
Radic. Biol. Med.2002;29:597-601.)
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Oxidative DNA Damage & Cancer
Figure : The individual value of
the urinary modified base
(8-OH-Gua) (Ref. Rozalski, R. et
al. Cancer Epidemiol. Biomarkers
Prev.2002;11:1072-5.)
Page 45
Figure: Correlation coefficient
between the level of 8-OHdGuo
in tumor tissues and the tumor
size (Ref. Foksinski, M. et al. Free
Radic. Biol. Med. 2000;29:597-601)
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Oxidative Stress & Cancer
Biomarkers of
Oxidative Stress
Colon cancer
patients (n = 45)
Control
group (n=55)
Plasma ascorbic acid (M)
29.45 ± 27.41
49.76 ± 29.24
Plasma a-tocopherol (M)
18.87 ± 14.50
24.69 ± 14.55
Plasma retinol (M)
0.80 ± 0.75
1.23 ± 0.61
Plasma uric acid (mg/dl)
3.73 ± 1.32
4.28 ± 1.13
8-oxoGuo/106 dG in lymphocytes
13.76 ± 7.19
9.57 ± 3.59
(Ref. Olinski, R., et al. Mutation Res. 2003;531:177-90)
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Acquired Immunodeficiency
Syndromes : Evidences
• Cells infected with HIV can enhance
production of superoxide anion
• HIV-infected patients : Studies
– Deficiency in SOD and catalase enzymes
– Decreased concentrations of antioxidant vitamins
– A significant increase in the level of 8-OHGua and
5-OHUra in lymphocytes -- apoptosis
– Vitamin supplementations lead to the reduction of
the level of oxidative DNA damage
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Oxidative Stress in HIV-Infected
Patients
Study Results :
Supplementation with
antioxidant vitamins
(vitamin A, E and C)
prevents oxidative
modification of DNA in
lymphocytes of HIVinfected patients
(Ref. Jaruga, P., et al. Free Radic. Biol. Med. 2002;32:414-20)
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Ischemia-Reperfusion Injury
• Ischemic – reoxygenation
– Cardiac ischemic-reperfusion
– Cerebral ischemic-reperfusion
• Tissue damages caused by excessive
production of free radicals
– High concentration of oxygen
– Low levels of antioxidants
• Prevented by antioxidant supplementation
Page 49
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Ischemia-Reperfusion Injury
ATP
i
s
c
h
e
m
i
a
Xanthine
dehydrogenase
Ca2+-dependent
protease
AMP
Xanthine
oxidase
Adenosine
O2-
Hypoxanthine/Purine
REPERFUSION
Xanthine/Hypoxanthine
TISSUE
INJURY
O2
XOD
O2 + H2O2
Fe2+
OH- +
 OH
O2.- + uric acid
O2
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Neurodegenerative
Diseases/Neurotoxicity
Diseases
Acute
Cerebral ischemia/
reperfusion
Traumatic brain injury
Chronic
Alzheimer’s disease
Parkinson’s disease
Huntington’s disease
Amyotrophic lateral sclerosis
Page 51
Evidences
O2.- and ONOO- increased, impaired
mitochondrial function
ROS increased, lipid peroxidation, protein
oxidation increased, antioxidant decreased
Oxidation of lipids, DNA, proteins increased,
induction of ROS by amyloid-
Oxidation of lipids, DNA, proteins increased
in substantia nigra
Oxidative damage increased in the basal
ganglia, ROS levels increased
ROS increased, oxidation of lipids, DNA and
proteins increased, mutant of SOD
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Cardiovascular Diseases
• Elevated level of 8-OHGua in the lesion of the
aorta wall in atherosclerotic patients
• Level of 8-OHGua in lymphocytes of
atherosclerotic patients was significantly
higher than in the DNA of control group
• Formation of oxidized LDL
– Direct action : Foam cell formation
– Indirect actions : Down regulates the base excision
repair (BER) pathway, leading to higher level of
8-OHGua [prevented by antioxidant vitamins]
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Atherosclerosis
(A) Oxidized LDL
stimulates monocyte
chemotaxis
(B) Oxidized LDL inhibits
monocyte egress from
the vascular wall
(C) Monocytes differentiate into macrophages that internalize
oxidized LDL, leading to foam cell formation
(D) Oxidized LDL also causes endothelial dysfunction and injury
(E) Oxidized LDL causes foam cell necrosis, resulting in the
release of lysosomal enzymes and necrotic debris
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Base Excision Repair (BER)
1.
Removal of the incorrect base by an
appropriate DNA N-glycosylate to
create an AP site (abasic site; the
position of the modified (damaged)
base)
2.
Nicking of the damaged DNA strand
by AP endonuclease upstream of the
AP site, thus creating a 3’-OH
terminus of adjacent to the AP site
3.
Extension of the 3’-OH terminus by a
DNA polymerase, accompanied by
excision of the AP site
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Aging
• AGING : a progressive accumulation of
changes overtime that increases the
probability of disease and death.
• Two main theories of aging “Aging theories”
• Programmed theory ~ a genetic timetable
• Damage theory ~ injuries that build up
overtime
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Free Radical Theory of Aging
• Aging ~ the cumulative
consequences of free radical
reactions
• Life-span experiments
– Relationship between
antioxidants, redox-sensitive
transcription factors and free
radical levels
– Age-related decline in
activation tresholds of
transcription factors and its
normalization by antioxidants
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Drug-Induced Toxicity
Doxorubicin
Page 57
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Chemical-Induced Toxicity
• Environmental pollutants : tobacco smoke,
dust, etc
• Organic solvents : benzene, carbon
tetrachloride, etc
• Other chemicals
• Detection of oxidative biomarkers as an
index of chemical exposure
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Measurement of Oxidative Stress
• Oxygen consumption
• Oxidative markers “footprints”
– Lipid peroxidation products (TBARs, lipid hydroperoxides, etc)
– DNA hydroxylation products (8-OHGua,
– Protein hydroxylation products (nitrosation products)
• Free radical detection
– Single photon counting
– Chemiluminescence
– Fluorescent probe
– Electron paramagnetic resonance spectroscopy (EPR)
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ANTIOXIDANTS
614 351 Toxicology
Supatra Porasuphatana, Ph.D.
Contents
• Oxidant-Antioxidant balance
• Biological actions of antioxidant defense system
• Antioxidant defense system
– Superoxide dismutase (SOD)
– Catalase
– Glutathione cycle/Glutathione peroxidase
– Diet-derived antioxidants & Low molecular weight
antioxidants
• Roles in the cellular protection against oxidative
stress & oxidative stress-related diseases
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Oxidant-Antioxidant Balance
Damage
(Pro-oxidants)
Page 62
Defense
(Antioxidants)
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Oxidant-Antioxidant Balance
Decrease of antioxidant defense system
Oxidative damage
Page 63
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Cellular Defense Mechanisms
• Isolation of generation sites of reactive
oxygen species
• Inhibition of propagation phase of
reactive oxygen species
• Scavenging of reactive oxygen species
• Repair of the damage caused by
reactive oxygen species
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Protection Against ROS Damage
• Direct protection against ROS
– Superoxide dismutase, Glutathione peroxidase, Catalase
• Non-specific reduction system
– Glutathione, Vitamin C
• Protection against lipid peroxidation
– Glutathione peroxidase, Vitamin E, -Carotene
• Sequestration of metals
– Transferrin, Lactoferrin, Ferritin, Metalothionein
• Repair systems
– DNA repair enzymes, Macroxyproteinases, Glutathione
transferase
Page 65
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Antioxidant Defense System
• Antioxidant Enzymes
– Superoxide dismutase (SOD)
– Catalase (CAT)
– Glutathione peroxidase (GPx)
• Endogenous non-enzymatic
antioxidants
– GSH, bilirubin
Page 66
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Antioxidant Defense System
• Exogenous antioxidant molecules
– -Tocopherol -- prevents oxidation of fatty
acids
– Carotenoids (-carotene, leutin, lycopene,
etc) -- destroy a particularly damaging form of
singlet oxygen
– Ascorbic acid -- radical scavenging, recycling
of vitamin E
– Bioflavonoids -- potent antioxidant activity
Page 67
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Superoxide Dismutase (SOD)
Function
2O2•- + 2H+
k ~ 2-4
x
H2O2 + O2
109 M-1s-1
• Only enzyme known to react with radical
• The presence of SOD implies O2.- produced in
cell during normal metabolism
• * SOD is a primary antioxidant enzyme
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Forms of SOD
Page 69
Procaryotic SOD
MW/Da
Fe-SOD
40,000
Mn-SOD
40,000
80,000
Subunits
2
2
4
Eucaryotic SOD
MW/Da
Mn-SOD
88,000
CuZn-SOD 32,000
EC (CuZn) 135,000
EC Mn-SOD 150,000
Subunits
4
2
4
2,4
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Intracellular Location of SOD
• CuZn-SOD
– Cytoplasm, nucleus, lysosomes
• Mn-SOD
– Mitochondrial matrix
• EC (CuZn)
– Plasma membrane, extracellular
• EC Mn-SOD
– Plasma membrane
Page 70
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Structure and Properties of SOD
• CuZn-SOD
– One of the most stable protein
– Inactivated by guanidine HCl, CN-,
diethyldithiocarbamate (DETC)
• EC-SOD
– Inhibited by CN-, azide, H2O2, SDS
– Located in extracellular fluids
– Suppresses inflammation
• Fe/Mn-SOD
– Not stable
Page 71
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Catalase (CAT)
Function : Removes H2O2
2 H2O2
2 H2O + O2
• Prevents lipid peroxidation
and protein oxidation
Page 72
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Glutathione Cycle
Glutathione ~ Glu-Cys-Gly
Reduced glutathione (GSH)
Oxidized glutathione (GSSG)
Function : gets rid of H2O2 or ROOH (hydroperoxide)
ROOH
Glutathione
peroxidase
ROH + H2O
Page 73
2 GSH
NADPH
Glutathione
reductase
GSSG
NADP
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Glutathione Biosynthesis
Two Step-Mechanism
1. By enzyme g-glutamylcysteine synthetase
L-glutamate + L-cysteine + ATP
L-g-glutamylcysteine +ADP + Pi
2. By enzyme glutathione synthetase
L-g-glutamylcysteine + glycine + ATP
GSH + ADP + Pi
Buthionine sulphoximine (BSO) inhibits g-glutamylcysteine synthetase
Cellular GSH
Page 74
increase sensitivity to toxicants
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Glutathione Peroxidase (GPx)
Function : Removes H2O2 & ROOH
ROOH + 2 GSH
ROH + H2O + GSSG
Deficiency in GPX leads to oxidative hemolysis
Protects against lipid peroxidation
*Selenium*
Page 75
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Low Molecular Mass Agents
• Compounds synthesized in vivo
– bilirubin, melatonin, lipoic acid, uric acid,
etc.
• Compounds derived from the diet
– Ascorbic acid
– Vitamin E
Page 76
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Ascorbic Acid
Antioxidant Function
Donate 1 e-
semidehydroascorbate (ascorbyl radical)
Relatively unreactive
Page 77
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Ascorbate-Glutathione Cycle
DHA + 2GSH
Page 78
ascorbate + GSSG
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Tocopherol
“Chain-breaking antioxidant”
Scavenges peroxy radical
Inhibits chain reaction of lipid peroxidation
Eight naturally-occurring substances
d--, d--, d-g-tocopherols
d--, d--, d-g-tocotrienols
Page 79
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Antioxidant Network
• Antioxidant network
Page 80
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Biological Properties of
Natural Antioxidants
• Natural antioxidants
– Polyphenols (phenolic, flavonoids), carotenoids,
lycopene, etc
• Electron donor property
– Ability of antioxidant to donate
electron to a species (free
reducing property
an
radical) –
– Antioxidant remains stable
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Basic Ring System of Flavonoids
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Basic Structure of Flavonoids
3’
2’
8
7
A
6
B
O
C
4’
2
5’
OH
6’
3
OH
5
O
HO
O
HO
OH
O
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Quercetin
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Two-Stage Oxidation of Quercetin
OH
OH
HO
.
R-O
O
O
R-OH
HO
O
HO
OH
.
O
O
R-O
O
O
HO
HO
OH
O
Orthoquinone
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Hydrogen-bond
stabilized
semiquinone
OH
R-OH
HO
O
.
O
HO
OH
H
O
O
HO
OH
O
Extended paraquinone
(J. Agric. Food Chem. 2003;51:1684-90)
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Roles of Antioxidants in Protection
Against Oxidative Damage
• Animal models
– Transgenic mice overexpressing SOD, CAT,
GPx show an increase tolerance in
oxidative damage (ischemia-reperfusion,
heart & brain injury, hyperoxia, adriamycin
and paraquat toxicity)
– Antioxidant gene knockout mice increased
susceptibility to oxidative damage
(ischemia-reperfusion, free radical
generation)
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Roles of Antioxidants in Protection
Against Oxidative Damage
• Human studies
– Aging (mitochondrial dysfunctions leads to
excessive production of free radicals – tissue
damage), age-related diseases (cataract,
cancer, etc)
– Chronic diseases (cancer, cardiovascular
disease, diabetes, neurodegenerative diseases,
inflammation, etc)
– Oxidative injury caused by chemicals, drugs,
etc
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SUMMARY
• Characteristics of free radicals/reactive
•
•
•
•
•
•
oxygen species
Endogenous/Exogenous formation of free
radicals
Oxidative cell damage (lipids, DNA, proteins)
Oxidative damage-related carcinogenesis
Antioxidants (types, functions)
Antioxidant network
Roles in the preventions against oxidative
damage
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References/
Suggesting Readings
• Halliwell, B., Gutteridge, J.C.M. (eds.) Free Radical in
Biology and Medicine. 3rd ed.
• Packer, J., Hiramatsu, M., Yoshikawa, T. (eds.) Antioxidant
food supplements in human health. Academic Press.
• De Zwart, L.L., et al. Free Radic. Biol. Med. 1999;26:202-
26.
• Roberts, L.J. II, Morrow, J.D. Free Radic. Biol. Med.
2000;28:505-13.
• Olinski, R., et al. Free Radic. Biol. Med. 2002;33:192-200.
• Mayne, S.T. J Nutr. 2003; 133 (Suppl 3): 933S-940S.
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